The present invention relates to a semiconductor device, and particularly relates to effective techniques applicable to a semiconductor device formed by mounting a semiconductor chip on one surface of a wiring board via a bump electrode and provided with a package structure in which resin is filled in a gap area between the one surface of the above wiring board and the principal surface of the above semiconductor chip.
A semiconductor device, formed by mounting a semiconductor chip on one surface of a wiring board via a bump electrode, and provided with a package structure in which resin is filled in a gap area between the one surface of the wiring board and the principal surface of the semiconductor chip, is developed as described on pages 14 to 19 of the April issue of Electronic Material published in 1996 by Industrial Research Association, for example. As the mechanical strength of the resin filled in the gap area between the one surface of the wiring board and the principal surface of the semiconductor chip can compensate that of the bump electrode in this semiconductor device, the bump electrode can be prevented from being damaged due to the difference in thermal expansion coefficient between the wiring board and the semiconductor chip. As the rear surface (opposite to the principal surface of the semiconductor chip) and the side face are exposed in this semiconductor device and the area in which the semiconductor chip is exposed to the air is large, the efficiency of heat radiation in which heat generated from the semiconductor chip is radiated in the air is higher, compared with a semiconductor device in which the semiconductor chip is sealed in a seal box, and compared with a semiconductor device which is mounted in a cavity formed by a package.
In the above semiconductor device, the heating value of heat generated from the semiconductor chip tends to be increased as the performance of a circuit system mounted on a semiconductor chip is enhanced. In the meantime, the plane size of a semiconductor chip tends to be large-sized as the performance of the circuit system mounted on the semiconductor chip is enhanced. However, the ratio in which the plane size of the semiconductor chip is increased is smaller, compared with the ratio in which the heating value of the semiconductor chip is increased. That is, the area in which the semiconductor chip is exposed to the air is not increased in proportion to the heating value of the semiconductor chip. Therefore, the efficiency of heat radiation in which heat generated from the semiconductor chip is radiated in the air is deteriorated.
The object of the present invention is to provide a technique which enables enhancing the efficiency of heat radiation of a semiconductor device provided with a package structure in which a semiconductor chip is mounted on one surface of a wiring board via a bump electrode and resin is filled in a gap area between the one surface of the wiring board and the principal surface of the semiconductor chip.
The above and other objects and new characteristics of the present invention will be clarified by the description in this specification and the attached drawings.
The brief description of the summary of the typical inventions disclosed in the present invention is as follows:
In a semiconductor device provided with a package structure in which a semiconductor chip is mounted on one surface of a wiring board via a bump electrode and resin is filled in a gap area between the one surface of the wiring board and the principal surface of the semiconductor chip, an aluminum nitride plate member formed in a larger plane size compared with that of the semiconductor chip, is arranged on the rear surface opposite to the principal surface of the semiconductor chip, and a fixing area on the one surface of the plate member opposite to the rear surface of the semiconductor chip is fixed on the rear surface of the semiconductor chip via solder. Further, a radiating fin made of aluminum is arranged on the above plate member via a thermally conductive elastic body or grease.
According to the above means, the plate member formed so that the outside size is larger than that of the semiconductor chip has a larger area in which the plate member is exposed to the air, compared with the exposed area of the semiconductor chip. The thermal conductivity of the plate member formed by aluminum nitride is high. Thermal conductivity from the semiconductor chip to the plate member is high in a fixed part between the rear surface of the semiconductor chip and one surface of the plate member via solder. Therefore, heat generated from the semiconductor chip is efficiently transmitted from the semiconductor chip to the plate member and the heat transmitted to the plate member is efficiently diffused flatly. Further, as the heat diffused on the plate member is efficiently transmitted in the air by a radiating fin made of aluminum, the efficiency of heat radiation in which heat generated from the semiconductor chip is radiated in the air can be enhanced.
As the area other than the area in which the plate member is fixed on the rear surface of the semiconductor chip is exposed to the outside, the exposed area can be increased, compared with a case that a plate member is fixed on a wiring board and a case that a plate member is fixed on a package.
As the difference in a thermal expansion coefficient between the plate member made of aluminum nitride and the semiconductor chip consisting of a silicon substrate is small, thermal stress generated due to the difference in the thermal expansion coefficient between the plate member and the semiconductor chip can be prevented from being generated even if the plate member is fixed on the rear surface of the semiconductor chip via solder.
As a plate made of aluminum nitride can be simply processed, for example cut by a machine, the cost can be reduced. Further, as a fin for increasing the heat radiating area is formed by aluminum, it can be cast, and a fin in a complicated shape can be obtained at a low cost.